Processes for manufacturing pieces basically comprising a first taping step and a second heat-forming step are well known in the aeronautic industry.
Layers of a composite material such as the prepreg, which is a mixture of fibrous reinforcement and polymeric matrix which can be stored, are placed in a suitably shaped mold/jig in the taping step.
This material can be in several forms and particularly in the form of fabric. Resin is generally partially cured or is taken to a controlled viscosity by means of another process called B-step for thermosetting matrices.
The composite material fabrics are not placed randomly, but rather they are arranged in each area in a number and with an orientation of their fibrous reinforcement, typically carbon fiber, determined according to the nature and magnitude of the stresses which the piece will support in each area.
Each area thus has a typical structure of the arrangement or stack of the fabrics. The difference in thickness between the different areas generates fabric drops, which requires having a fabric model for each piece clearly establishing how it must be arranged on the mold/jig during the stacking process. The final result is a planar laminate with areas of different thickness.
In the second step, a heat-forming process is carried out which basically consists of placing the planar laminate resulting from the first step on a jig or mandrel with suitable geometry and applying heat and vacuum according to a certain cycle so that said laminate is adapted to the shape of the jig.
By following processes of this type, several C-shaped pieces made of composite material have been manufactured in the aeronautic industry such as torsion box spars and ribs of horizontal stabilizers for airplanes, provided that the differences in thickness between adjacent areas are not very large since otherwise unwanted creases are formed in the radii of the slopes joining these areas.
In the known art, the pieces with large differences in thickness between two adjacent areas, such as for example an airplane wing spar with an area for anchoring the landing gear which must support a large load, are either manufactured from metal or, if they are manufactured with composite materials, metal angle bars were used to join webs and planar skins of composite materials.
The present invention is aimed at solving the problem set forth by the mentioned limitation for manufacturing pieces made of composite material formed with large differences in thickness between adjacent areas.